Triangle Keelback Xenochrophis trianguligerus a semi-aquatic, lowland forest species... entered cave via stream no doubt, but not a cave snake per se... identified courtesy Tony Sebastian - seen at broken jar cave - a large - 600 mm x 1.5 cm and a baby snake - 200 mm x 0.6 cm both swam in water in cave, red markings looked dangerous
http://www.ecologyasia.com/verts/snakes/triangle_keelback.htm
http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN2480 According to University of Adelaide Non-Venonous with dry bite
Medium in length, cylindrical, elongate moderately slender bodied snake with a moderately long tail. Can grow to a maximum of about 1.35 metres. Head is distinct from neck. Eyes are large in size with round pupils. Dorsal scales are usually strongly keeled ( smooth on outer one or two scale rows ) with apical pits. Ventrals rounded. Dorsal scale count usually 19 - 19 - 17
Feeds mainly on small rodents, birds, frogs, toads, tadpoles and fish